The tropical tuber crops contain starch as the major component and thus act as important source of starch. Except cassava and to a smaller extent sweet potato, starch from other tuber crops has not been exploited for industrial applications partly because of difficulty in the extraction of the pure starches and partly because of non-availability of information about the properties of these lesser known starches. This review attempts at collating data available on the physicochemical and functional characteristics of the tropical tuber starches, highlighting their unique properties and potential field of applications. The physicochemical properties like granule shape and size, X-ray diffraction (XRD) patterns, amylose content, or content of non-starchy components, show considerable variation among the tuber starches. In addition, factors like genetic origin, environmental conditions and age of the plant also influence the properties. The starch granules of Colocasia esculenta and Dioscorea esculenta tubers are very small whereas those of Canna edulis are very large. XRD patterns of yam starches are generally ‘B’, while the aroid starches possess ‘A’ patterns. DSC gelatinisation temperatures are low for cassava starch and high for the aroid starches. The functional characteristics like viscosity, swelling power and solubility also depend on a number of factors such as varietal variation, method of extraction, processing conditions and instruments used for analysis. Viscosity is high for cassava and C. edulis starches, but low for most aroid starches. Clarity is good for cassava and yam starches compared to the others. Digestibility also varies among the starches. The diversity available in the tuber starches shows that some of the starches can be used in place of chemically modified starches available on the market. The realisation of their importance can help in value addition of these neglected crops and also provide starch with special properties for specific applications.

Physicochemical and Functional Properties of Tropical Tuber Starches: A Review

Pasting, paste, and gel properties of starch–hydrocolloid combinations

Pasting and rheological properties of native and anionic tapioca starches as modified by guar gum and xanthan gum

Effects of non-ionic polysaccharides on the gelatinization and retrogradation behavior of wheat starch

Publisher Summary
The functional properties of starch depend on a number of integrated factors, which include polymer composition, molecular structure, interchain organization, and minor constituents such as lipids, phosphate ester groups, and proteins. Chemical, enzymic, and physical modification of starch, with either preservation or destruction of the native granule, broaden the functionality-imparting properties of different starches. The greatest challenge is to relate physicochemical properties and functions of starch with information on various levels of structure. There is a diversity of structures depending on starch source, amylose–amylopectin ratios, lipid, moisture and plasticizer contents, and thermo-mechanical histories. In addition to difficulties in describing and quantifying the structural morphology of starch materials, the ultra structural level of starch also presents a great challenge. This chapter discusses some aspects of phase transition behavior and other material properties of starch, particularly as they pertain to the structural order and interactions of the starch polysaccharides with water, lipids, and other solutes. Understanding the thermally induced structural transitions of starch is helpful in controlling its physical properties and processing behaviors (e.g. plasticization, viscosity), as well as in designing products with improved properties (e.g. texture, stability). The description of the state and phase transition behavior of starch systems is focused on with an emphasis on their molecular organization and their response to various environments (temperature, solvent, other cosolutes). Selected material properties are also discussed in an effort to demonstrate structure–function relationships of this biopolymer mixture in pure systems and in real food products.

Chapter 8 – Structural Transitions and Related Physical Properties of Starch

Effect of hydrocolloids on the rheological properties of wheat starch

The carbohydrate composition of winged bean has been studied,
The seeds contain about 42.2% total carbohydrates of which starch
alone accounts for 36.2%. The total monosaccharides constituted
2.7% and were identified as glucose (1.17%) and fructose (1.5%);
oligosaccharides amounted to only 0.61% and were identified as
sucrose, raffinose, stachyose, and verbascose, on a dry defatted
basis. The cold water soluble gum of winged bean contains glucose
and xylose as the major sugars together with a small amount of
arabinose while hot water soluble gum was found to be a glucantype
polymer. Hemicellulose A consisted of glucose, xylose, and
arabinose (15.5:9:1) whereas hemicellulose B consisted exclusivelyo
f glucosein dicatingt hat it is alsoa glucan-typep olymer.

Carbohydrate Composition of Winged Bean (Psophocarpus tetragonolobus)

The Isolation and physico-chemical properties of the yam, elephant starch have been investigated. The yield of extracted starch was about 80%. The starch exhibited single stage swelling and moderate solubility in water and low resistance to solubilization by DMSO. The amylose content of the starch was found to be 24.5%. The viscosity decreased considerably during cooking at 90°C. The amylolytic susceptibility of the native and gelatinized starch with human salivary α-amylase und glucoamylase have also been investigated.



Isolierung und physikalisch-chemische Eigenschaften der Starke aus Yam, Elephant (Amorphophallus campanulatus).



Die Isolierung und die physikalisch-chemischen Eigenschaften der Yam-Elephant-Starke wurden untersucht. Die Starkeausbeute betrug 80%. Die Starke zeigte eine einstufige Quellung, masige Loslichkeit in Wasser und geringen Widerstand gegenuber der Losung in DMSO. Der Amylosegehalt der Starke wurde mit 24,5% ermittelt. Beim Kochen bei 90°C verringerte sich die Viskositat betrachtlich. Die amylolytische Angreifbarkeit sowohl der nativen als auch der verkleisterten Starke mit menschlicher Speichel-α-amylase und mit Glucoamylase wurde ebenfalls untersucht.

Isolation and Physico-chemical Properties of Starch Extracted from Yam, Elephant (Amorphophallus campanulatus)

Isolation of a neutral linear xylan from guar seed husk

Guar gum in its native form exhibits a very good thtckening capacity and hence is used
as a thickener or agent for 'binding' water in food, cosmetics and toiletries, in
pharmaceuticals and in the mining, paper and textile industries (Glicksman 1976). This
communication reports the effect of introducing an anionic carboxymethyl group upon
the thickening capacity of guar gum and the related secondary functional properties of
stabilising foams and suspensions. Compared with native guar gum, carboxymethyl
guar gum with a degree of substitution of 0.68 exhibited a higher viscosity and an
enhanced ability to stabilise foams and suspensions. Both native and carboxymethyl
guar gum induced a non-Newtonian pseudoplastic behaviour to casein (100 g litre- ')
suspension. At the same time only carboxymethyl gum gum containing suspensions
above I g fitre-' exhibited measurable yield value.

S. Umadevi Sajjan

Papers

Effect of hydrocolloids on the rheological properties of wheat starch

Carbohydrate Composition of Winged Bean (Psophocarpus tetragonolobus)

Isolation and Physico-chemical Properties of Starch Extracted from Yam, Elephant (Amorphophallus campanulatus)

Isolation of a neutral linear xylan from guar seed husk

Functional properties of native and carboxymethyl guar gum